1. Field of the Invention
The present invention is related to a wireless communication, more particularly to a method of transmitting a warning message in a multiple component carrier system.
2. Related Art
In a common wireless communication system, although the bandwidth of uplink and the bandwidth of downlink are differently set up, only one carrier is taken into consideration. Even in 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), the number of carriers constituting uplink and downlink is 1, and the bandwidth of uplink and the bandwidth of downlink bandwidth are in general symmetrical to each other on the basis of a single carrier. However, it is not easy to allocate a large frequency bandwidth except some regions in the world. Accordingly, in order to efficiently use small sliced bands, a carrier aggregation technique for producing the same effect as that a logically large band is used by binding a plurality of physically non-continuous bands in the frequency domain is being developed. The carrier aggregation technique includes, for example, a technique in which system bandwidth of 100 MHz is supported by using multiple carriers.
Recently there has been an interest to ensure that the public has the capability to receive timely and accurate alerts, warnings and critical information regarding disasters and other emergencies irrespective of what communications technologies they use. As has been learned from disasters such as earthquakes, tsunamis, hurricanes and wild fires; such a capability is essential to enable the public to take appropriate action to protect their families and themselves from serious injury, or loss of life or property. This interest to enhance the reliability, resiliency, and security of Warning Notifications to the public by providing a mechanism to distribute Warning Notifications over wireless systems is the impetus for the Public Warning System (PWS).
If multiple downlink carriers are aggregated, PWS messages are broadcast from each downlink (DL) carrier. Hence, the same PWS messages will be duplicated on all DL carriers which are aggregated.
To avoid duplicated transmission of PWS messages from all aggregated DL carriers, eNB may broadcast PWS messages only from one of the aggregated DL carriers, in particular from non-backward compatible carrier or extension carrier. However, UE staying at a DL carrier which does not broadcast PWS messages cannot receive the PWS messages.